AB0746 CHANGES IN DIAGNOSING GIANT CELL ARTERITIS OF THE TEMPORAL ARTERY OVER A 7.7 YEAR PERIOD
Authors: M. H. Röchter, S. Thiesbrummel, H. Marchi, C. Fuchs, M. Rudwaleit
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Temporal artery biopsy (TAB) was the diagnostic reference standard for decades in giant cell arteritis (GCA). Evidence-based EULAR recommendations regarding the use of imaging techniques in diagnosing GCA have been published in 2018 [1]. Accordingly, the use of colour Doppler ultrasonography (CDUS) should "complement the clinical criteria for diagnosing GCA, assuming high expertise and prompt availability of the imaging technique" [1]. However, sensitivity and specificity of CDUS showed substantial variation between studies (2), with the investigator's expertise assumed to be a major contributing factor [1]. <h3>Objectives</h3> To study changes in the use of CDUS and TAB as diagnostic procedures for suspected GCA of the temporal artery over a period of 7.7 years in a single rheumatological centre. <h3>Methods</h3> Patients who presented to our rheumatological department between 10/2014 and 06/2022 were retrospectively identified either via a final diagnosis of GCA (ICD-10 codes M.31.4, M31.5, M31.6) or by the coded procedure of TAB (OPS 1-587.0 or 1-587.x). CDUS was performed by rheumatologists using GE Healthcare S5 machine from 2014 until spring 2016, and thereafter GE Healthcare LogiqE9 machine. A positive CDUS was defined by a non-compressible halo sign and hypoechogenic thickened vessel wall in any of the temporal arteries. We compared the frequency of use and results of CDUS and of TAB for confirming a clinical diagnosis of GCA of the temporal artery in three time periods of 2-3 years each (2014-2016, P1; 2017-2019, P2; 2020-2022, P3). Statistical significance of changes in relative frequencies was assessed via Fisher's exact test. <h3>Results</h3> Of 158 patients, we excluded 48 patients for the following reasons: diagnosis of aortitis or Takayasu vasculitis by other diagnostic means (n=16), final diagnosis other than GCA but undergoing TAB (n=24), already existing diagnosis of GCA with affection of the temporal artery prior to first presentation (n=7), and incomplete data sets (n=1). Of 110 GCA patients analysed, the mean age was 76.2 yrs (range 55 to 91 yrs), and 72 patients (65.5%) were female. All but one patient underwent CDUS (99.1%). Over the entire study period, the proportion of positive CDUS findings increased from 45.8% in P1 to 80.6% in P3. Conversely, the proportion of TAB evaluations decreased from 88% in P1 to 71.4% in P2 to 16.7 % in P3. In all three time periods, conducted TAB evaluations were largely positive: 77.3% in P1, 74.3% in P2, and 83.3% in P3 (Figure 1). In P3, 29 out of 36 (80.6%) GCA patients had a positive CDUS and were diagnosed based on CDUS alone, all of them without consecutive TAB. Only 6/36 patients (16.7%) underwent TAB: 5 patients received a positive TAB after doubtful CDUS, 1 patient received a doubtful TAB after negative CDUS. The proportion of patients who were diagnosed with GCA after positive CDUS and without TAB among all GCA-diagnosed patients that underwent CDUS of the temporal artery significantly increased when comparing P3 vs. P1 (p&lt;0.001) and P3 vs. P2 (p&lt;0.001), but not for P1 vs. P2 (p=0.2). Due to small sample size and involvement of several rheumatologists who gained experience in CDUS over the study period, an independent effect of exchanging the ultrasound machine could statistically not be assessed. <h3>Conclusion</h3> A significant change in using CDUS alone for diagnosing GCA of the temporal artery has taken place between 2014 and 2022, with substantial reduction of TAB evaluations especially after having obtained positive CDUS results. This change is likely due to increased expertise and confidence of the examiners (rheumatologists) in CDUS evaluations on appropriate ultrasound machines over time. Yet, data from the most recent time period indicate the ongoing need for TAB as an effective diagnostic tool in the few cases of inconclusive CDUS and high clinical suspicion of GCA. <h3>References</h3> [1]Dejaco et al. (2018) EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice. Ann Rheum Dis 77(5):636-643 [2]Buttgereit. (2016) Polymyalgia Rheumatica and Giant Cell Arteritis: A Systematic Review. JAMA 14;315(22):2442-58 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.